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Setting video modes in protected mode

Does anyone know where to find information about setting video modes in protected mode? I am going to write a small driver for my protected mode command line operating system for other programs to use. I expect this has to be done using ports and any information would be appreciated.

asmosprog@hotmail.com

Comments

  • DariusDarius Posts: 1,666Member
    : Does anyone know where to find information about setting video modes in protected mode? I am going to write a small driver for my protected mode command line operating system for other programs to use. I expect this has to be done using ports and any information would be appreciated.
    :
    : asmosprog@hotmail.com
    :

    Newer VBEs have a protected-mode entry point. That would be your best bet for this. Wander around www.vesa.org until you find their VBE3 specification. Without it, then yes you'd probably need to use ports and they'd probably be fairly card specific.

    "We can't do nothing and think someone else will make it right."
    -Kyoto Now, Bad Religion

  • blipblip Posts: 756Member
    My (failed) OS would find a video mode and then switch to it in real mode before switching to pmode. This allowed VESA 1.x compatibility and it would resort to mode 13h if no VESA BIOS was present. It also had an access table so that it woud have all of the video mode's information on hand. Couldn't you take my approach? Anyway, if you do want to switch with ports, here's a BIOS source code that might help get you started: http://www.programmersheaven.com/zone5/cat20/15830.htm. Also, look for PC-GPE because it has programming tutorials for specific cards along with tons of other information.
  • asmosprogasmosprog Posts: 54Member
    Thanks for the information, I will just set the video mode in real mode before switching to protected mode. Or maybe just switch to virtual 8086 mode like a DOS box and then back to protected mode.

    asmosprog@hotmail.com
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